Neurons from the superior cervical ganglia of newborn rats will be isolated and grown in culture by methods previously described by this laboratory. The major points of interest will be: 1. To study further the cholinergic synapses formed by there neurons on each other; special attention will be given a) to pharmacological investigation of the acetylcholine receptors and b) to the question whether individual neurons synthesize both acetylcholine and catecholamines. Physiological, histochemical and electronmicroscopical methods will be used. 2. The influence of non-neural cells, especially cells from the heart, on the time course and extent of formation of the cholinergic synapses.